Fuel cells are capable of highly efficient microgeneration, and thereby enable easy building of a system which utilizes thermal energy generated in power generation. Thus, recent years have seen more and more fuel cells used for home cogeneration systems to achieve high-energy efficiency. The cogeneration system is a type of on-site electric power supply system as exemplified by a photovoltaic system, and supplies electric power in connection with a system power supply operated by an electric company. When in-home electric power load is within the supplying capability of a cogeneration system, all electric power for the electric power load is supplied by the cogeneration system. When in-home electric power load exceeds the supplying capability, the system power supply covers the deficiency. The cogeneration system generally has a display unit which displays a current electric power generated by the cogeneration system and electric power purchased from the system power supply so that the users can know contribution of the cogeneration system.
It is technically possible for the on-site electric power supply to supply electric power independently of the system power supply. It is thus desired that the on-site electric power supply independently operate as an emergency power supply when a power failure occurs due to a disaster or deficiency in supply capability of an electric utility. When an on-site electric power supply connected to a system power supply is used as an emergency power supply, the on-site electric power supply generally needs to be parallel off the system power supply and turned off upon detection of failure of the system power supply so that the safety of the network of the system power supply can be secured. On the other hand, the fuel cell needs to be supplied with electric power to activate the fuel cell before starting power generation so that the fuel cell is heated to a predetermined temperature and a pump to fuel the fuel cell is turned on.
There is proposed an independent operation support device which allows an on-site electric power supply system such as a fuel cell system to operate independently. For example, in the event of a power failure, such an independent operation support device connects only between an on-site electric power supply and an in-home electric power load, and supplies electric power required for activation of the on-site electric power supply (see Patent Literature (PTL) 1).